1. Field of the Invention
The present invention relates to novel electrostatic transfuse belts, or intermediate transfer belts, for receiving toner images from a photoreceptor toner image forming member and transfusing said images to a copy member such as a paper copy sheet to form fixed images thereon.
2. State of the Art
Electrostatographic printing machines such as photocopiers, laser printers, facsimile machines and the like incorporating intermediate transfuse systems and belts are well known in the art, as illustrated by embodiments of U.S. Pat. Nos. 5,922,440; 5,991,590; 5,434,657 and 5,459,008, for example. Transfuse systems and copy machines incorporate an intermediate continuous belt having a surface which is receptive to the electrostatic transfer of toner images from a photoreceptor belt or drum, generally by applying a charge to the intermediate belt which is opposite to the charge of the toner images. The toner-imaged intermediate transfuse belt is then continuously cycled through the pressure nip between a heated roller and a pressure roller, in surface contact with a copy sheet whereby the toner images are heat-fused to the surface of the copy sheet and transferred from the surface of the transfuse belt when the belt and copy sheet exit the pressure nip.
In electrostatographic printing machines in which the toner image is transferred from the intermediate transfer member to the image receiving substrate, it is important that the transfer of the toner particles from the intermediate transfer member to the image receiving substrate be substantially 100 percent. Less than complete transfer to the image receiving substrate results in image degradation and low resolution. Completely efficient transfer is particularly important when the imaging process involves generating full color images since undesirable color deterioration in the final colors can occur when the color images are not completely transferred from the intermediate transfer member.
Thus, it is important that the intermediate transfer member surface has excellent release characteristics with respect to the toner particles. Conventional materials known in the art for use as intermediate transfer members often possess the strength, conformability and electrical conductivity necessary for use as intermediate transfer members, but can suffer from poor toner release characteristics, especially with respect to higher gloss image receiving substrates, and poor adhesion to the substrate, particularly under the effects of heat.
Although continuous application of a liquid release agent to the belt surface increases toner transfer, the transfer member outer layer can swell upon repeated addition of the release agents. For example, it has been shown that silicon rubber performs well as a transfer layer, but swells significantly in the presence of hydrocarbon fluid release agents and loses adhesion to the support belt, particularly when heated. Also, release properties have been shown to decay from repeated interaction with certain release agents such as hydrocarbon release agents.
U.S. Pat. No. 5,459,008 discloses an intermediate transfer member in combination with a thin film coating of a release agent material comprising a polyolefin, a silicon polymer, or grafts of these polymers, and mixtures thereof.
U.S. Pat. No. 5,922,440 discloses an intermediate toner-transfer belt having a polyimide film support, an adhesive binder layer or prime coat, a polymer layer such as a fluoropolymer, polyimide or silicone rubber, and an outer release layer of a similar polymer. While the optional adhesive binder layer provides some degree of improved mechanical adhesion to the polyimide film substrate, the mechanical adhesion to the belt support and/or to the polymer layer is subject to failure after repeated use in the transfusion transfer process whereby the useful life of the belt is reduced.
A need remains for an intermediate transfer member that exhibits substantially 100 percent toner fusion and transfer, without system failure, to image receiving substrates having glosses ranging from low to very high, over a prolonged life of use at elevated temperatures without delamination and breakdown. Further, a need remains for a combination of a transfer member surface layer and a release agent that does not result in significant swelling and separation of the outer layer of the transfer member. In addition, it is desired to present a transfusion belt in which the transfer properties of the belt do not significantly decay or degrade over repeated reuse at elevated temperatures.
Finally, it is desirable that the release surface of the transfusion belt remains smooth and glossy after repeated reuse in order to continue to produce 100% transfer of the toner images and the formation of copy images which have glossy surfaces and have a pleasing appearance over the lifespan of the belt.
The present invention relates to an improved reusable intermediate transfuse belt for use in the electrostatic process of forming toner images thereon and heating sufficiently to fuse the images and transfer them as glossy-surfaced images to a copy sheet in contact therewith, which belt is resistant to heat-degradation and delamination over an extended life of repeated reuse.
The novel transfuse belts of the present invention have an elastomer-coated, continuous seamless fabric belt support and a conformable release layer of an elastomer polymer having a smooth glossy surface, characterized by the presence of an intermediate hydrolyzed polyfunctional moisture-cured silicone primer layer which is chemically-bonded to both the elastomer-coated belt support and to the elastomer release layer present thereon to prevent any separation or delamination of the elastomer release layer over prolonged reuse of the transfuse belt at elevated fusion temperatures up to at least about 200xc2x0 C.